The present invention relates generally to an arrangement for adjusting the axial positioning of a pair of colinear shafts in a power transmission apparatus and, more specifically, to an endplay adjuster assembly disposed between the colinear input shaft and mainshaft of a four-wheel drive transfer case.
Many power transmission apparatuses (i.e., transfer cases, transmissions, transaxles, etc.) of the type used in the driveline of motor vehicles are equipped with a pair of colinear and relatively rotatable shafts and a clutch mechanism for transferring drive torque therebetween. For example, a conventional transfer case 10 is shown in FIG. 1 to include a housing assembly 12, an input shaft 14, a planetary gearset 16 driven by input shaft 14, a mainshaft or rear output shaft 18, and a range clutch 20 operable for selectively coupling rear output shaft 18 for rotation with one of input shaft 14 and an output 22 of planetary gearset 16. Transfer case 10 also includes a front output shaft 24, a drive sprocket 26 fixed to front output shaft 24, a drive sprocket 28 rotatably mounted on rear output shaft 18, a chain assembly 30 interconnecting driven sprocket 26 to drive sprocket 28, and a mode clutch 32 operable for selectively coupling drive sprocket 28 to rear output shaft 18. A shift mechanism 34, under the control of the vehicle operator, is connected to range clutch 20 and mode clutch 32 to facilitate coordinated actuation thereof for establishing various drive modes.
Input shaft 14 is shown to be rotatably supported in a front housing section 12a by a front bearing assembly 36. Likewise, rear output shaft 18 has a pilot hub 38 formed on its forward end which is rotatably supported by a needle bearing assembly 40 that is retained in a pilot bore 42 formed in input shaft 14. The rearward end of rear output shaft 18 is rotatably supported from rear housing section 12b by a rear bearing assembly 44. Thus, input shaft 14 and rear output shaft 18 are colinear and supported for rotation about a common rotary axis "A". In addition, a cup plug 46 seals pilot hub 38 of rear output shaft 18 relative to input shaft 14.
During assembly of transfer case 10, an inner race 36a of front bearing assembly 36 is slid onto input shaft 14 until it abuts a radial shoulder surface 48 formed thereon and a snap ring 50 is then mounted in a circumferential groove 51 formed in input shaft 14, thereby retaining front bearing assembly 36 on input shaft 14. Input shaft 14 is then installed into housing section 12a such that an outer race 36b of front bearing assembly 36 engages a radial shoulder surface 52 of housing section 12a and then a snap ring 54 is mounted in a circumferential groove 55 formed in housing section 12a, thereby axially positioning and restraining input shaft 14 relative thereto. Alternatively, front bearing assembly 36 could be initially mounted to housing section 12a with input shaft 14 thereafter installed in front bearing assembly 36 and snap ring 50 mounted in the groove 51 formed in input shaft 14.
During continuation of the assembly of transfer case 10, an inner race 44a of rear bearing assembly 44 is slid onto rear output shaft 18 and is axially restrained between a pair of snap rings 56a and 56b mounted in circumferential grooves 57a and 57b formed in rear output shaft 18 respectively. Thereafter, rear output shaft 18 is installed in housing section 12b such that outer race 44b of rear bearing assembly 44 abuts a radial shoulder surface 58 of housing section 12b and then a snap ring 60 is mounted in a corresponding groove 61 formed in housing section 12b. Alternatively, rear bearing assembly 44 could initially be installed in housing section 12b with rear output shaft 18 slid into its inner race 44a followed by installation of snap ring 56b. As seen, a hole 62 in housing section 12b provides the requisite access to install snap ring 60 and is then sealed by a rubber housing plug 64. Once pilot hub 38 of rear output shaft 18 is mounted in pilot bore 42, housing sections 12a and 12b are then interconnected in a manner well known in the art.
In such colinear shaft layouts, the machining tolerances for the groove location, groove width, shoulder locations, and the snap ring width, in conjunction with the necessary design assembly clearances, may stack up to permit an excessive amount of axial movement (i.e., "endplay") between input shaft 14 and rear output shaft 18 Such endplay has been recognized as contributing to driveline noise or clunk and may also cause increased wear of the driveline components.